The present invention relates to a method for operating a motor of a motor-driven power steering (MDPS), and more particularly, to a method for operating a motor of an MDPS, in which when an error occurs in any one of three phases in an inverter circuit of the MDPS, the other two phases are used to drive a motor so as to maintain an assist power.
In general, a MDPS provides an assist torque in a driver's steering direction using an electric motor such that the driver smoothly handles a steering wheel.
The MDPS automatically controls the operation of the electric motor according to a driving condition of a vehicle, unlike an existing hydraulic power steering (HPS). Therefore, the MDPS may improve the steering performance and steering feeling.
Typically, the MDPS drives a three-phase motor to provide an assist power. Therefore, the MDPS includes an inverter circuit for operating the three-phase motor.
When an error occurs in any one phase of the inverter circuit while the vehicle is driven, an improper assist power may be provided to interfere with driver's steering. Therefore, the MDPS is switched to a manual mode.
However, when the MDPS is suddenly switched to the manual mode, providing the assist power is suddenly stopped. Therefore, the driver may feel a significantly different steering feeling.
For example, when the MDPS is suddenly switched to the manual mode in a state where the vehicle is cornering at a low speed, the steering feeling felt by the driver suddenly gets heavy so as to degrade the driving safety of the vehicle. In this case, an accident may occur.
Furthermore, in order to block the phase of the inverter circuit where an error occurred, a relay and a capacitor must be used. Therefore, the cost inevitably increases.